For 30-plus years, Waukesha Enginator® Units Provide 99.999997% Uptime Meeting Building’s Energy Needs

(ST. LOUIS) – For the past 33 years, a major office building in the heart of this historic city has kept a secret from its occupants: it’s never received a bill from the local electrical utility. Thanks to a very well-designed on-site power plant utilizing eight Waukesha engines the Laclede Gas Office Building has been making its own electricity reliably and efficiently. And, through co-generation, the engines are also handling heating and cooling chores.

Now into their fourth decade of continuous operation, the Waukesha Enginator® engine/generator units are still running well thanks to a conscientious preventive maintenance program. Three of the engines have accumulated more than 180,000 hours of operation on the same blocks and crankshafts. During this time the engines offered near 100 percent availability with virtually no unscheduled downtime.

Building Opened in 1970

As the soaring ’60s were coming to an end, four smaller buildings were demolished in downtown St. Louis to make room for the 31-story, 500,000-square-foot building. Opened in 1970 with a bank on the main floor and second floor along with gas utility offices, an accounting firm, trade associations, two restaurants and a fitness facility occupying the rest, it was the first high-rise building of its kind in St. Louis (glass and metal instead of masonry) and typical for the era. Some 1500 people come to work here each weekday.

Although built and owned by a developer, the local gas company was the major tenant wanted a total energy plant on site. This was agreed to and the building has always made its own power and has never been connected to the local utility grid. The fact that the Laclede co-generation system has functioned so well over three decades and continues meet the building’s needs is a testament to the people who designed and installed it. The original installation was done by Charles Equipment Co., a Waukesha Engine distributor based in Addison, IL. Even today it is the only St. Louis office building that meets all its electrical, heat and air-conditioning needs with natural gas fueled engines.

“The Laclede building functions as its local utility, since it’s not hooked up to the local provider, Union Electric, and buys its own gas through a 6-inch pipeline,” says Robert Creech, who joined the building’s energy operations department as a stationary engineer in 1970 after leaving the Air Force where he was radar technician. A six-month assignment to straighten out the engine-room controls turned into a 30-year career where he’s now in charge of five people in the power plant and two in building maintenance. “We purchase about 5000 ccf. of gas daily during work week, about half that amount on weekends. From 7 a.m. to 9 p.m. on weekdays, 7 a.m. to 1 p.m. on Saturdays we’re producing 40,000 kWh each day with around 23,000 kWh needed per day for the rest of the weekend. The demand is higher during summer months in order to operate cooling towers and variable air volume in the HVAC system. Summer load can hit 27000 kW with gas consumption at 6500 ccf.”

Third-Floor Power Plant

The Waukesha Enginator®-based system provides electricity, heat, hot water, low pressure steam to power chillers for the air-conditioners and chilled water. Interestingly, the building relies on the same number of engine/generator units, packaged by Waukesha Power Systems, that it started with thirty-three years ago. Located in the third floor power plant are two Waukesha L7042GU engines rated at 550 kW and four Waukesha L5108GSIU turbocharged engines at 800 kW each. The building also has two Centrivac centrifugal chillers located on the 31st floor, also powered by Waukesha H2476GU engines each rated 350 tons.

“The entire system was designed and built very well, especially when you factor in the personal computers, copy machines, printers, faxes, variable-frequency drives on air-handling equipment and pumps, plus myriad other energy-consuming devices that are common in today’s offices but hardly thought of three decades ago” Creech continues. “The power plant is on third floor, which is unusual as a basement location is more common. However, because a bank is one of the original tenants that space was needed for vaults. The office workers on the floor below are not aware that there are gensets hard at work directly above them. Also, the tenants are unaware their building is off the grid. Once, during a downtown power outage 20 years ago, the building was lit up during a blackout and some people wondered why this was happening.

“The local power company’s grid is very reliable and its rates are relatively inexpensive. During a natural gas price peak in 1999, thought was given to hooking up to the grid and using city-supplied steam from a downtown power plant. Around nine different scenarios, from complete dependence on the local grid to partial reliance, were considered. Because the capital expense was absorbed many years ago, it was determined that it was still better to continue generating power on-site. Even with today’s fluctuating gas prices, it’s still more economical. Generating our own power costs us about a nickel per kWh including maintenance costs, which hover around a penny. The utility’s average cost is seven cents per kWh. When you factor in the free HVAC from the ‘waste’ heat from the engines, we’re doing far better with co-generation.”

Ebullient Cooling System

The system uses ebullient (literally “boiling liquid”) cooling of the engines to make low-pressure steam. It takes water from the engine’s cooling jacket and routs it to a boiler where it’s heated by the engine’s 1100° F exhaust temperature. To produce 10 psi of steam, the engines must maintain 240° F jacket water temperature. The most demand for steam actually is in the summer months for use by the absorption chiller that can require 18,000 pounds of steam per hour. With ebullient cooling, the heat recovery unit functions as a heat exchanger so there’s no need for the traditional “radiator.”

The resulting mixture of steam and hot water is also used to provide hot water for use by the occupants. The steam is also piped to a 1,000-ton lithium bromide absorber that produces approximately 800 tons of 42° F chilled water for air-conditioning using the steam generated by the Enginators. The remote-located chillers, mentioned earlier, supplement the system. With York AC and lithium bromide units, a total of 17,000 tons of AC is provided. The system uses EM (Electric Machinery) generators and Killebrew heat recovery units.

It was Creech’s idea to use another source of heat, taken from the engines’ oil coolers, in a novel way: during the winter months it’s routed to an “air curtain” above a rear entrance to the building.

“The system returns about 95% of the condensate water back to the engines to start the process all over again,” Creech explains. “Altogether, we get 800 tons of chilled water; 5 ½ pounds of steam per kWh produced. To put it another way, for each 100 cubic feet of gas consumed we get about 7 ½ kW and about 41 pounds of steam. The system is around 76% efficient, far greater than just generating electricity alone, which we estimate is done at about 30% efficiency.

Single Outage in 33 Years

“In 33 years, we lost power once in 2000, due to a technician shorting out the DC power. The power went down for about 30 seconds, but everything came back on line with no problems. There is no backup power on site, everything is dependent on our six engines. Ebullient cooling was more common in ’70s and it means that there’s no water pump for the jacket water. Movement of coolant depends upon changes in temperature and is more common when steam is required from a generating system.”

In the early ’80s, because of a spike in natural gas prices the local utility was approached about linking the Laclede building to its grid. “The proposed cost for transformers and lines was over a million dollars then, so it would be much more today but there’s interest whenever the gas utility proposes a rate hike,” Creech notes.
“Because we’re the only building in the area that generates its own power I conduct a lot of tours for people considering installing their own co-gen system. While many are local, I’ve had some visitors from Latin America and even Saudi Arabia.